Testing device for telephone-exchange systems



Jan, 13, 1925. 1,522,856

A. s. BERTELS TESTING DEVICE FOR TELEPHONE EXCHANGE SYSTEMS Filed Nov. e, 1922 e sheds-sheet 1 www mm k w. S S l W, h b A QS n Y r ,J A d d m., m QS S. /M l@ a. 0 n f k A y QQ uw b .www um@ 6 2 si@ z, m r 2 S s. b 1 .M-m mw @s H6 V E m a, H n m r f N mm1 RPG Ew. www Aww w S N n m m m, X m w P J .nmmm M.

Jan, 13, 1925.

f 1,522,856 A. s. BERTELs TESTING DEVICE FOR TELEPHONE EXCHANGE SYSTEMS,

Filed Nov. 6, 1922 6 Sheets-Sheet 3 Mvenor: Arno/d Berre/s Jan. 13, 1925. 1,522,856

A. s. BERTELs Y TESTING DEVICE FOR TELEPHONE EXCHANGE SYSTEMS Filed Nov, e, 1922 6 Sheets-Sheet 4 y www@ Jan. l3 1925.

A. S. BERTELS TESTING DEVICE FOR TELEPHONE EXCHANGE SYSTEMS 6 Sheez-Sheet 5 wwe/'fon Arnd/d Seffe/s. V 4

Nov. 6. 1922 Jan, 13, 1925. 1,522,856

A. S. BERTELS TESTING DEVICE FOR TELEPHONE EXCHANGE SYSTEMS Filed Nov, e, 1922 .e Sheets-Sheet 6 Tha/sanas 6 Hundreds Ven/bf.-

Ar/fa/a S @effe/s.

Patented dan. 13, i925.

ARNOLD S. BERTELS, OF TENAFLY, NEW' JERSEY, ASSIGNO'R T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TESTING DEVICE FOB TELEPHONE-EXCHANGE SYSTEMS.

Application filed November G, 1922. Serial No. 599,229.

To all tf1/"20m t may concern:

Be it kno-wn that I, ARNOLD S. BnR'rELs, a citizen of the. United States of America, residing at Tenafly, in the county of Bergen Aand State of New' Jersey, have invented certain new and useful Improvements in Testing Devices for Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

rihis invention relates to a telephone exchange system, and more particularly to testing circuits for use therein in testing call indicatortrunks and call indicator ycircuits. o f

ln a telephone exchange system during the period when thel exchange is being changed from a manual to an automatic operating basis, there are certain oiiices which are equipped with machine switching apparatus and function for calls local thereto on a full mechanical basis, and other oliices which temporarily are. equipped only with regular manual equipment. In certain exchange arcas there may also be offices which for certain traiiic reasons it may not be desirable or economical to change from manual to machine switching equipment. Such manual ofices, in order that connections. originating in machine switching offices may be terminated therein, are equipped with operators positions in which appear trunks incoming from all machine switching ofiices having access thereto. Each such operators position is also equipped with a call indicator mechanism upon which may be recorded, under the control of the calling subscriberin the originating oiiice, the number of the line desired in such terminating manual oflice. Call indicator mechanism of this character is well known in the art and may be of the type disclosed, for example, `in the patent to A. E. Lundell and Edgar H. Clarke No. 1,464,084, issued August 7, 1923.

ln order that at all times the call indicator trunks incoming to a manual office and the call indicator mechanism associated therewith shall be maintained at the highest possible degree of efliciency, it is desirable that means be provided for making special and routine tests of such trunks and mechanism from time to time. It is therefore the object of the present invention to provide testing mechanism and circuits for making special or routine tests of any trunk circuit or call indicator mechanism of a manual oflice .of the character above described.

rl`he principal feature of the invention resides in the provision of a portable testbox which may be connected at will by cord circuits to any call indicator trunk circuit or to any call indicator mechanism of an office, and which is provided with a key- )card upon which any line designation may be recorded7 and an impulsing switch for simulating the operation of the impulsing switch of a regular oiiice sender whereby the control circuits and indicator lamps are caused to function in the standard manner to indicate the recorded designation.

A further feature of the invention resides in the provision of means in the test box for testing the operation and adjustment of certain relays of control circuits or trunk circuits under test simulating the best and worst conditions under which such relays 'rust operate in actual service.

A further feature resides in the provision of means for transmitting individual impulses of light yor heavy positive and negative current for testing the sensitive and marginal relays of a` call indicator control circuit.

A. still further feature resides in the provision of circuits for testing the accuracy with which the call indicator control circuit and trunk circuit under test function in the selection, application and tripping of ringing current when applied to call a. particular party on a party line.

These and other features of the invention will be more apparent from a consideration of the following description and appended claims.

Referring to the drawings, Figs. l to 6, inclusive, when arranged in the order illustrated in Fig. 7, disclose so much of the circuits of a manual call indicator operators apparatus and of the testing device which embodies the invention as is necessary to an understanding of the invention.

Fig. l shows a test line to which connection may be established by any call in` dicator trunk of the manual ofce, such as the trunk of Fig. 2, having ringers similar to the ringer-s of a four party subscribers line, together with jacks and patching cords for `enabling connections to be established between the testing device. of Figs.

- dende and the control circuitV of Fig. 5, Y or between the testing device and-the testing wound spring motor which is releasedto perline and trunk circuit of Figs. 1 and 2.

Fig. 2 shows `a. 'call-indicator trunk circuit vincoming from a` machine switching ofiice for extending connections tofsubscribers lines and arranged to cooperate with the *call "indicator disclosed -inv Figs. '5 and 6.

Figs. 3) and 4 taken together show the V'circuits of a portable testingdevice for inakirg tests of call indicator circuits, such as shown m Fig. 2, Vor call indicator mechanism, such as shown in Figs. 5 and 6. Fig.

shows'the keyboard of .the testing device, and Fig. eshows'the impulsing switch, con- -itrolling relays, keys and lamp signals of the vitesting device.

Y Fig. ov fsh'ows y the' control `circuits of a call indicator mechanism arrange-d to be associa-ted ywith any of the trunk circuits, such as shown in 2, of an operators position, vand operative in response to code impulses Vrtranemitted thereto over a trunk circuit incoming from a machine switching ofce or,v

from the testing device of Figs. 8 and 4.

Figi 6. shows Ithe selecting relays and numerical Ylamps lof the call indicator for visually informing the manual operator of the designation f of the called Y line.

General description of circuits md appa-mtas.

4The call indicator trunk circuit of Fig. 2 and thecall indicator mechanism shown 1n Figs. '5 and 6 are of the same generall type as disclosed inthe aforesaid patent, differing therefrom only in the provision of means A forselecting and applying ringing current to the calling strands of the trunk circuit in accordance with thefdesignation of the party linestati'on, indicated by the Ystations lamps on the call indicator, andin the provision of lan additional marginal relay in the im-V pulsing circuit of Fig. V5. lTwo marginal control relays areprovided in order that the call indicator may be employed with trunk circuits of two groups, the trunk circuits of Vone of said groups having loop resist-ancres within certain speciiied limits, over which one of said marginal relays is adjustedto function, and the trunk circuits of the other of such groups having loop resistances within other specified limits, over which the other of said marginal relays is adjusted to function.

The keys of the keyboard, shown in Fig. 3, with the exception of keys 800, 808 and. 3,09, are of the mechanicallyl locking type, the key in any vertical row being maintained conducting two typesV 'of tests.

desired to test a call indicatormechanism, .such for example, as that shown in Figs. 5

operated until restored by the depression of another key in the same row. The sequence switch, the cams of which are shown at the C. F. Baldwin No. 1,127,808, issued February 9, 1915,differing therefrom only in .that

the ,cams there@ cperatedpby a manually mit asinglerevolution' ofthe switch through the operation of the release magnet 400.

rlthe provision of'a spring driven sequence which arentfequipped with power equip.

ment of the machine switching type.

The;

switch 2150, shownat the right of Fig. 4, may'v be of the type disclosed in the patent toG.

,Brown No. 11,155,640, issued October 5, 1915,

being driven by a spring motor, which when wound up and released, causes a single rev,V

olution of the cams thereof.

The testing device of Figs. Sjand 4, as previously mentioned, may be employed for Whenvit is and 6, the jacks ofthe testingjdevice 100, V108 and 104 are vconnected by cordcircuits,

known as patching cords, 105, 108 and 109 to'jacks 110, 111 and 112, respectively, in-I dividual to the call indicatorY to be tested,

and the jacks 101 and 102 of the testing device by patching cords 106 and 107 vto powerv Vjacks 1141 and 115. Following the connection of the testing device Vto the indicator mecha I vnism, the spring driven sequence switch is wound vup, the designation of the first test number is recorded `upon Vthe keys ofthe keyboard, and thel start key 300 isoperated.

' The sequence switch upon being released through the operation of the start key tra-ns-k mits the proper code of impulses toselectively lightthe lamps v of the'indicator in accordance with the designation recorded on the keyboard. In .this manner the test man may v' check the accuracy of operation of the mdicator by noting the designation,recorded by vthe depressed keys ofthe keyboard and by vthe lamps which are lightedat the Acall indicator mechanism. If the iirstr'test call is successively indicated, anothertest' call withV the same designation is made, but under different circuitcondition's; VIf thev indicator functions properlyV the designation' of the VYnext ,test number is recorded andthe testingv In thisV manner 'digits of the-test numbers are so' selected that e the control circuit and lamp relays of the in dicator under test areoperated in all possible combinations.

Table of `test ca lylynufmbers.

lT11. n. o T. U. sm.

o 1 2 s o i 2 i3 4 R 2 3 4 5 J 3 4 5 er n 4 5 e 7 M t e 7 's W c c 7 s 9 o 7 a 9 0 R a 9 o 1` i e `o 1 R Should it be. desired to test a trunk circuit,isuch" as shown in F ig. 2, the jacks -100 to104, inclusive, are connected by patching cords 105 to 109, inclusive, to jacks 113 to '117,inclusive, The spring driven sequence same manner as` they would be operated upc-ira call incoming thereto from a ma- 'chinevswitching othce. When the operator assigns the trunk to her indicator by dew pressing the assignment key 211', the impulsing switch of 'the testing` device is released, and transmits to the call indicator associated withthe Vtrunk circuit impulses for setting the indicator in accordance with the designation set upon the4 keyboard of the testing device. Thisl designation being 00000, the operator knowing that this designation indicates that the call has come to her trunk circuit from the testing device, plugs into the jack 227 of the test line. Upon the connection of the rtrunk vcircuit with the test line, ringing current is selectively applied thereto to ring one of the bells associated With the test line, whereupon the test man may proceed to make Whatever tests are necessary in connection with the ap aaratus of the trunk circuit under test. houldthe test man` desire to test the trunk circuit for applying ringing current necessary for ringing any one of the four bells of a party line, he may vdo so by successively set-ting up numbers on the keyboard, each number comprising four numerical digits O and a different station digit, either J, R,` M or W.

Y Testing u. cfa-Z7 indicator y71Lecha-msm.

lt `vill be assumed that the test man desires to test the call indicator mechanism disclosed to Figs". 5 and 6, and for that pur.- pose connects the jacks 100 to 104, inclusive, with jacks 110, 114,115, 111 and 112 by the cords105 to 109, inclusive, and disconnects all incomingr trunks at the operators position with' Which the call'indicator mechanism is associated from the call indicator to be tested, and connects such trunks to the emergency equipment so that all calls which may come in to the operators position during the test may be handled by the emergency. equipment without tying up ltheoperators position.

' For the purpose ot' this description it will loe assumed that the marginal rela-yv 500 ot' the call indicator is adjusted to operate over interoiiice trunk loops off-2100 to 2600 ohms resistance, and that the marginal relay 501 is adjusted to operate over loops of 800 to 1700 ohms resistance', and that the indicator mechanism is to be tested first withrelay 500,V key 401 ot the testing device heilig for this purpose in its normal position. T he test man thereupon depresses the key 302 for inserting the lowest voltage and the highest resistance into the impulse circuit extending from the testing device to the call indicator mechanism, in series with marginal relay 500, for simulating` the worst operating condition under Which the marginal relay 500 would be designed to operate in actual servvice.'V The test man thereupon depresses the thousands key 303, the hundreds key 304,4

the tens key 305, the units key 806 and the stations key 307 Afor recording upon the keyboard the designation of the irst test number appearing in theaforementioned table,

01230,I afnd'ivinds the motor of the spring` driven sequence switchr This sequence switch is restrained from returning to normal by the detent on the armature of magnet 400. The circuits of the testing device are now in condition for making the first test, and the test man thereupon depresses the start key 300.

With the start key 300 depressed and the trunk testing' key 402 and disconnect keys 808 and 309 in normal position, av circuit is established for relay 403 of the testing device'and relay 502 of the indicator under test, which may be traced from battery, through the Winding of relay 502, conductor 508, sleevev of ack 111, sleeve strand oi cord 108, sleeve of jack 103, conductor118, the normal Contact of spring 404 of key 402, conductor 405, the'right contact of key 308, conductor 310, the lett. Winding' of relay 403,

Aconductor 406, the right contact of key 300,

conductor 311, the normal contact oli spring 407 of key 402, conductor 408, ring of jack 103, ring strand of cord 108, ring ot' jack 111, conductor 119, and thence to ground by parallel paths, one extending through the winding of relay504 and the other through the normal contact of relay 505, conductor 506, to ground at the left armature and contact of relay 507. Relay 504 being shunted at this time by direct ground at the contact of relay 507 does not energize, but relays 403 and 502 energize. yRelay 502, upon energizing, connects ground to the holding conductors 508 and 509 through the armature contacts of relay 510 for furnishing operating and locking ground for the various relays of the indicator mechanism, as will appear hereinafter. Relay 403, upon energizing, locks through bot-h of its windings over a circuit from ground at the normal contact of spring 409 of key 402, conductor 410, the inner right armature and front contact of relay 403, thence -through both windings of relay 403 and over the circuit. previously Vtraced to battery through the winding of relay 502. Relay 403 is thus maintained energized in series with relay 502 independent of 4start key 300, which may now be released.

Relay 403 also closes a circuit for relay 411 in series with relay 505, which may be traced from battery through the winding of Yrelay 411, conductor 412, the left armature .strand of cord 108, the tip of ack 111, conductor 120, winding of relay 505, the ground at the right armature and back contact 'of relay 507. Relay 505,upon energizing, opens Ythe shunt around relay 504 and relay 411 Y closes a circuit for the sequence switch release magnet 400, which latter circuit may be traced from battery, through the winding of release magnet 400, the normal contact of key 416, the intermediate armature and front contact of relay 411, the right contacts of cam 417 (l), the -left armature and back contact of relay 418, conductorv 419, 'and thence to ground through the left contacts of keys 308 and 309.

cams of the sequence switch to the control circuit of the call indicator mechanism, which will be traced hereinafter in connection with the vtransmission of'k code impulses of the first test number. The removal of the shunt from around relay 504 is without function at this time, since upon the release kof start key 300, the circuit previously traced through the winding of relay 504 is open at the contactsfof key 300.

1t has been assumed that the stations digit of the first test number was 0, and that the No. 0 stations key 307 was depressed. It will be noted from an inspection of this key that its contacts are without function, and that therefore during the revolution of the seque-nce switch of the testing device, the impulsing circuit is unmodified while it is rotating from position 1 thro-ugh position 3 and through position 4%, and that therefore light negative impulses are transmitted over the impulse circuit only in' positions 3% and 5%. Vhen, therefore, the sequence switch reaches position 33/4, a circuit is established which. may be traced from ground at the A ring contact of jack 114, the ring strand of cord106, the'ring contact of jack 101, conductor 121, the upper contact of sequence Relay 411. also establishes an impulse circuit from the inner left armature of relay switch cam-1420 theloiiter left arma-V Winding of negative polarized"relayll5f14,

winding of marginal relay7 r500, conductor 515, outer left armature and back contact of relay 511, conductor 516, ring of vjack 112, ring strand of cord 109, ring of jack 104,

conductor 123, normal contact of key 401,l

conductor 423, resistance elements,y 312 to 318, inclusive, left contact of key 302, c0n ductor 319, normal contact of key 320, conductors 321y and 424, right armature and front Contact of relay 411, upper contact -of sequence lswitch cam425 (3%)', high resistance element 426, conductor 427, ring of jack 102, ring strand of cord 107, ringlof jack 115, leftarmature and front contact of relay 124 to 45 Volt battery 126 through the armature and back Contact of relay 125. It is to be noted that at this time relay 124 is .energized over a. circuit vextending from battery, through its winding, the sleeve of jack 115, sleevestrand of cord 107, sleeve of jack 102, to ground. Y

The. current flowingoverthe circuit previously traced through the high resistance 426 is therefore of light strength and of negative polarity, causing only the energization of the negativelypolarizedrelay 514, relay 50,0 not receiving suflicient current to cause its energization. Since at this time relay 502A is energized and has connected ground to conductor 509, a circuit is established' from ground on conductor 509 through the armature contact of relay 514, the normal contacts associated with the 511, the left armature and back contact of relay 517,

winding of relay 518, to battery through the leftwinding of relay 517. Relay 518 energizes in this circuit,fbut relay 517 does not receive suficient current to cause its energization. Relay 518, upon energizing, closes a circuit from battery, through the leftwinding vof relay 517, the winding of relay 518, the lay 517, the right armature and front oontact of relay 518, to ground on conductor s.

509. Relay 517, however, does not energize at thisv time since its right hand winding is shunted through the contact of relay 514. Relay 518 at its right armature and front contact also closes a circuit for transfer relay 519, which may be traced from battery, through the winding of relay 519, left armature andback contact of rel-ay .520, right armatureand front contact of relay. 518 to ground on conductor 509. Relay 519, upon at* tracting its armatures, establishes a locking right winding of recircuit for itself from battery, through its winding, the winding of relay 520, the right armature and contactv'otv relay 519, to ground on conductor 509. Relay 520, however-,does not energize at this time since its winding is shunted by a direct path to ground, through the contact of relay 518. As soon, however, as the sequence switch ot the testing device leaves position 3%, relay releases and removes the shunt from around the ri ,qht winding of relay 517, whereupon relay 517v energizes in series with relay 518. l

TWhile the sequence switch passes through position v51/2L, the circuit through relays 500, 513 and 514 previously traced is again closed, and relay 514 again energizes and upon attracting its armature, closes a circuit from battery, through the left winding" of relay 517, left armature and front contact of relay 517, normal contacts associated with the inner left armature of relay 511, contact ot relay 514, to ground on conductor 509. lThis direct circuit to ground shunts the winding of relay 518, causing it to deenergize and release its armatures. Upon the release of its right armature, the shunt around the winding of relay 520 is opened, but this relay is still maintained shunted over the inner right armature and iront` Contact of relay 517. When the sequence switch moves out oic position 51/4, relay 514 releases its armature and opens the circuit through the left winding of relay 5,17. Relay 518 being at this time deenergized, no other circuit exists for relay 517, and consequently this relay becomes deenergized. l,Vhen relay 517 releases its armatures the shunt around the winding of relay 520 is removed and this relay energizes in series with relay 519. It. will be noted that none ofthe stations relays 521 to 525,r inclusive, ha c been operated,

`4'.nce the thousands digit `of the first test number is also 0, and as the No. 0 thousands key 303, which has been depressed, has no effective contacts, the impulsing circuit controlled by the sequence switch is unmodified Iit rotates from position 5% through position 6 andfroin. position 6% through position' 71/2, therefore as it passes positions and 81/,C light negative current is supplied to the impulse circuit above traced. frs thel sequence switch passes through position 6%, relay 514 energizes and causes the operation o't relay 518 in the manner previonsly described. Relay 518 prepares an energizing circuit for relay 517 and establishrsa circuit for transfer relay 526 which may be traced trom. battery, through the winding ot' relay 526, the left armature and back contact of relay 527, lett armature and t'ront contact oliv relay 520, the right armature and front Contact of relay 518, to ground on conductor 509. Relay 526, upon energizing, closes a locking circuit for itself extending through itswinding, the winding oit relay 527, the inner right armature and contact of relay 526, to ground on conductor hut relay 507 being shunted at thistime through contacts ot-relay 518 ydoes not ener- ILize in this locking circuit. When the sequence switch leaves position 6%, relay 514 deenergizes and removes the shunt from around the right winding of relay 517, whereupon relay 517 energizes in series with relay 518. v

As the sequence switch passes through position 81/1, relay 514 again energizes and establishes the previously traced circuit through the left winding f of relay 517, whereupon relay 518 being shunted, deenergizes. As soon as the sequence switch leaves position 8%., relay 514 again deenergizes, opening the holding circuit of relay 517 andy causing its deenergization. Since at this time relay 518 is deenergized, the winding of relay 527 is no longer shunted and this relay energizes in the locking circuit of relay 526. fis two light negative impulses have beei'itransniitted to the indicator mechanism it will be noted that none of the thousands lamp relays 600 to 603, inclusive, have been operated.

VVhenihe sequence switch of the testing device reaches position 9 withthe No. 1 hundreds key 304 depressed, an impulse of positive current is transmitted through the windings of relays 500, 513 and 514 over a circuit which may be traced from the nongrounded pole of battery 126, the armature and back contact or relay 125, the left armature-and front contact of relayl24, ring of jack 115, ring strand'o'f cord 107, ring' of jack 102, conductor 427, resistance 429, resistance 428, upper contact o'l1 cam 430 (9 te 103,4), upper contact o1 cani 481I (834 to 11). conductor 432, right contact of key 304, conductors 322 and the upper contact of cam 433 (8f/, to 91/2), the lowercontact of cam 435 the outer lett armature and trout. contact of relay 411, conductor 421, lett armature and back contact of relay 413, conductor 422, tipot jack 104, tip strand of cord 109,"tip ot jaclr 112, conductor 122, inner right armature and bach contact of relay 511, conductor 512, windings oitl relays 513, 514 and 500, conductor 515, outer left armature and back contact of relay 511, conductor 516, ring of jack 112, ring strand of cord 109,v ring of jack 104, conductor 123, normal contact of key 401, conductor 423, resistances 312 to 318, inclusive, left contact of key 302, conductor 319, contact of key 320, conductors 321 and 424, right armature and front contact of relay 411, lower contact of cam 420 (9), conductor 121, ring of jack 101, ring strand of cord 106, ring of jack 114*v` to ground.V Due to the inclusion of the high resistance 428, a weak impulse/of `relay 513 energizes. Y

va circuit from the grounded conductor 509, Y armature and contact oit relay 513, left arcurrent of theproper polarity is transmitted, and only the positively polarized Relay 513 completes mature and back contact of relay 518, left armature and front contact of relay 519,

Vleft armature and front Contact of relay 526, outer' left armatureand back contact of relay 528, conductor 530, left winding of hundreds lamp relay 604, to battery. Relay 604 becomes energized and closes a holding circuit. for itself from battery, through its two windings in series, contact and inner vright armature of said relay, to grounded conductor 508. As the sequence switch leaves position 9, the impulse circuit is opened and relay513 deenergizes.

As the sequence switch passes through position 9%, it closes a circuit from the nonvgrounded pole ot'battery 126 aspreviously traced through resistance 426, upper contact of cam 425 (9%), the right armature and front contact' of relay 411, thence as previously traced through the windings of relay 500, 513 and 514, outer left arinatureV and front contact of relay 411, the upperk 1 armature and back contact of relay 529, the

left armatures and front contacts of relays 527 and 520, the right armature'and front contact of relay 518, to ground on conductor 509. Relay 528 attracts its armatures and completes a circuit from battery, through the windings of relays 528 and 529 in series, front contact and inner right armature of relay 528, to grounded conductor 509. Re lay k529, however, does not energize since its winding is shunted by the contacts of relay 518. As the sequence switch leaves pofsition 9%, the impulse circuit above traced 'opened and relay 514 deenergizes to permit the energization of relay 517 in series with relay 518. y i r Y As the sequence switch passes through po sition 11%, a circuit is again closed through 'the windings of` relays 500,513 and 514,

throughY the upperl contacts of cams 420 and ,425', and a wealrimpulse'of current is trans mitted of the proper polarity to again cause the energization of polarized relay 514. Relay 514, upon energizing, closes a short circuit around the winding of relay 518, caus-v ing this latter relayto release. As the sequence switch moves out of position 111/4, re-

lay 514releases its armature to permit the,

Ydeenergization of relay 517., When relay 517 becomes deenergized, the' short circuit which up to this time has been maintained around the winding of relay 529 is removed. Relay 529 thereupon energizes and locks in serieswith relay 528'. At the time relay 528 energized, a circuit was established for the 0 stations lamp 531, it being recalled that nonerot the stations lamp relays were operated as the result ofV the transmission ot the stations code ot impulses. This circuit may be traced from battery, lamp 531, outer left armature and back contact of relay 521, inner left arma-ture and backV contacts ot relays 523, 524 and 525, conductor 532, to ground at the inner left armature and 'iront contact of relay 528.

As the sequence'switch passes through position 12%, since at this time the No. 2 tens key 305 is depressed, -a circuit is effective for relays 500, 513 and 514, which may bc traced from the non-grounded pole of battery 126, thence as previously described through low resistance 429, the lower Contact of cam 430 (12% to 13), the lower contact of cam 434 (11% to 14), conductor 435,right contact of key 305, lconductors 324 and 325,

previously, traced through the windings of relays 500, 513 and 514 to the outer leitY armature and front contact of relay 411, the upper contact of cam 420 (12%), to ground at ack 114. The impulse of current transmitted in this circuit is strong in character since only the low resistance 429 is included, both high resistances 426 and 428 being eX- cluded, and,l therefore causes the energization of marginal relay 500. Further, the polarity `of the impulse is such as to cause the energization of relay 514. Relay 514 attracts its armature and closes the circuit described .for the energization ot relay 518. Relay .518 inturn closesa circuit Afrom battery, through the winding oi. transfer relay 533, theleft armature and back contact of relay 534, the left armatures and front conf tacts of relays 529, 527 and 520, right armature and trontfcontact of relay 518, to grounded conductor 509. Relay 533 energizes and closes a locking circuit for itselt extending through its winding, the winding of relay 534, the inner right armature and front contact of relay 533, to grounded conductor 509, Relay 534 does not energize, however,as long as either of the relays 517 or `518 is operated. Relay 500 completes a circuit from grounded conductor 509, armaf ture and contact of relay 500, outer right Vcontacts of cam 425 thence over the circuit armature and back contact of relay 517. s

inner right armatures and front contacts ot relays 520, 527 and 529, inner right armature and back contact of relay 534, conductor 535, left winding of the tens lamp Vrelay 609, to battery. Relay 609 energizes and locks in a circuit from battery with both its windings in series, its inner right armature 130 1 ,masse relay to become energized in series lwith re-f lay 518.

The sequence switch in moving through position 141/, again closes a circuit through relays 500, 513 and 514 from the nongrounded pole of battery 126, as previously traced through resistance 426, rthe upper contact ot cam 425 (14%),the right 'arma ture and 'front Contact of relay 411, thence as traced through the windings of relays 500, 513 and'514, to the outer left armature and tront contact of relay 411, the upper cont-act ot cam 420 (141/4), thence as previously traced to ground at jack 114. `Since resistance is Yincluded in this circuit, ya weak impulse therefore transmitted of the polarity necessary to cause the energization of relay 514. Relay '514 closesv a shunt circuit tor causing the deenergization of relay 518, 1n moving out of position 14%, the sequence switch opens the impulse circuit and relay 514 releases permitting the release ot relay 517 Relay 517 Vand relay 518 now both being deenergized, the shunt around the winding of relay 534 is ,removed and this relay energizes in the locking circuit of relay 533. i

As the sequence switch passes through position 15 with the No.` 3 units key 306 depressed. a circuit is established for relays 500, 513 and 514, which may be traced from theV non-grounded pole of battery ,126, as previcu'isly' described, through the low resistance 429, resistance 42-8, the upper contact o1 cani 430 (15 to 16%), the upper contact ot' cani 434 (14%.to 17), conductor 436, the right contact o1' key 306, conductors 326 and 327, lower contact of cam 437 (15), thence over the circuit previously traced through the windings of relays 500,' 5`13and 514, returning through the lower contactv of cam 420 (15), to groun'drat jack 114. Due

to the inclusion of high resistance 428, a

weak impulse ot' current is transmitted and only the positively polarized relay 513 energizes. Relay 513 completes a circuit from grounded conductor 509, armature and contact otrelay 513, lett armature and back contact of relay 518, left armatures and front contacts ot relays 519 and 526, outer lett hand armatures and front contacts of relays 528 and 533, conductor 536', left winding ot units lamp relay 612r to battery. Relay 612, upon energizing, closes a holding circuit 'for itse'ltl ytrom battery, through its two windings in series, its inner right armature and Contact, to grounded conductor 508.l As the sequence switch leaves position 15, the impulse circuit is opened and relay 513 deenergizes.` i

The sequence switch in passing through position 15% closes a circuit through relays 500, 513 and 514., which may be traced from the non-grounded pole or battery 126, thence as previously described through low resistance 429, the lower contact of cam 430 (153/, to 16), the upper contact of cam (14%l to 17), conductor 436, right contact of key 306, conductors 326 and 327, the upper contact ot cam 437 (15%), thence as previously traced through the windings of relays 500, 513 and 514, returning over the upper contact of cam 420 (153/1) to ground at'jaolr114. The impulse of current transmitted in this circuit is strong in character since only the low resistance 429 is included, ancl'resistances 426 and 428 are both excluded, and therefore causes the energization or" marginal relay 500. Further, the polarity ot the impulse is such as to cause the energization of relay 514. Relay 514 attractsits armature and closes the circuit previously described tor energizing relay 518. Relay 518 in turn closes a circuit from battery, through the winding of transfer relay 537, lett armatures and front contacts ot relays 534, 529, 527 and 520, the right armature and contact of relay 518, to grounded conductor 509. Relay 537 energizes and closes alcol-:ing circuit for itself extending through its winding, winding of relay 511 and the inner right armature and contact of relay 537, to grounded conductor 509. Relay 511 does not energize, however, as long as keither of the relays 517 or 518 is operated. Relay 500 completes a circuit from grounded conductor 509, armature and contact of relay, 500, outer right arma'- ture and back contact of relay 517, inner right armatures and Vt'ront contacts of relaf/S520, 527, 529 and 534, conductor 538, to battery through the Vlett Winding of units lamp relay 613. Relay 613 energizes and locks in a -circuit from battery, through both of its .windings in series,l its inner right armature and contact, to ground on conductor 508. 11s the sequence switch leaves position 15%., the impulse circuit is opened and'relays 500 and 514 become deenergized.

Relay 514fupon deenergizing, removes the shunt from around the winding of relay 517,"permitting this relay to become energized in series with relay 518.

The sequence switch in moving through position 171/A again closes the circuit through relays 500, 513 and 514 from the nongrounded pole ot' battery 125, thence aspreviouslyl traced through resistance 426, upper contact ot' cani 425 (17%), the right armature and front contact of relay 411, thence as traced through the windings ot relays 500, 513 and 514, returning through the :outer left armature and front contact of relay 411, the upper contact of cam 420 (171/4), thence to ground at jack 114. As

the resistance 426 is included in this circuit,`

a weak'impulse is therefore transmitted of the polarity necessary to cause the energization of relay 514. Relay 514 closes a shunt circuit for causing the d-een-ergization of ree lay 518 in the manner previously described.

1n moving out of position 17 1g, the sequence switch opens the impulse circuit and relay 514 releases, permitting the release of relay 51,7. Relay/s 517 and 518, now both being deenerglzed, the shunt around the winding of ,relay 511 is removed, and this relay enerv..gizes Ain' the locking circuit of r-elay 537.

The lamp relays 604, 609, 612 and 613 have now been energized preparatory to causing the ,display of the test number 01230 upon the lamps of the indicator, if, as assumed,

the indicator mechanism has functioned acfltions 18 to- 181/4, inclusive, closes a circuit for the cut-off relay 418, which circuit may be traced from battery, through the Vwinding of relay 418, the left contacts of cam 417 (18 to 18%) to ground. Relay 418, upon energizing, locks over its left armature and front contact, conductor 419, to ground through the left normal contacts of lreys 308 and 309, and closes a circuit from ground on conductor 419, through its outer right armature i and front contact, through the back contact of relay 439, and supervisory relay 438, to battery, and opens the circuit of release magnet 400 of the sequence switch at the back contact of its left armature so that the release magnet cannot again be operated when the sequence switch reaches its normal position until after the disconnect key 308 has been depressed. 'The lighting of the supervisory lamp 438 at this time indicates that the test number has been recorded upon the vlamps of the indicator mechanism.` When the sequence switch reaches position 1 with magnet 400 deenergized, the detent on theV armature of magnet 400 engages a notch in the disc 480 on the shaft of the sequence switch arresting the'sequence switch.

At the indicator vunder test upon the ener-v gization of relay 533 during the transmis sion Vof the tens code of impulses, a circuit was established from ground at the inner left armature of relay 533,'thence by parallel paths through the winding of relay 539, to battery, and through the left armature and back contact of relay 540 and t-he winding Vof slow to release relay 541, to battery. Relay 539, upon energizing, closed a circuit vfor the No. 0 thousands lamp 617, which may be traced from battery, the right armature and front contact of relay 539, conductor 542, the inner right armature and back contact of relay 603the inner left armature and baclrcontact of relay 601, the outer rightV armature and bach Contact `of relay 600, the left armature and back contact of relay 602, lamp 617, the outer right armature and back contact of relay 601, the outer left armature and back Contact of relay 600, the outer right armature and back contact of relay 602, conductor 616, toground at the left armature of relayr539. A circuit for the No. 1 hundreds lamp 618 was also established by relay 539 as follows: battery, right armature and front contact of relay 539, conductor 543, the innergright armature and back contact of relay 607, inner left armature and back contact of relay 605, the outer right armature and front contact of relay 604, lamp 618, normal contacts of the Vouter left armature of relay7 605, the outer left armature and back contact of relay 607, conductor 619, to ground at the left armature and front contact or relay 539.

During the transmission of the units code impulses, relay 537 energized as previously described, and at its outer right hand armature closed a circuit for relay 540, whichL may be traced from battery through the winding of relay 540, outer right armature and contact of relay 537, to ground at thev inner left armature and contact of relay 533. Relay 540, upon energizing, opened the circuit of .relay 541, which Vbeing slow to release, after a predetermined interval which is designed to give sufficient time for the transmission of a final strong positive impulse where such an impulse is required, closed a circuit which may be traced from ground 'at its armature and back contact, through'the right armature and contact of relay 540, conductor 544, the winding of relay 507,conductor 545 to battery through the winding of relay 546. Relays 507 and 546 both energized, relay 546 closing a locking circuit for itself and for relay 507 which may be traced from battery, through the windings of relays 546 and 507, the inner leftV armature and contact of relay 546, conductor 547, the outer right armature and ontact of relay 537, to ground at the inner left armature and contactfof relay 533. A circuit is now established for the No. 2Y tens lamp 620, which may be traced-from battery, through the inner left armature and front contact of right armature and back contact of relay 610, conductor621, the'outer right armature and contact ofrelay 537, toground at the inner left armature and contact ofY relay 533.

A circuit is also established for the No. 3 units lamp 622 as follows; battery, right armature and contact of relay 546, conductor 549, the. inner right armature and back contact of relay 615, the inner left armature and front contact of relay 613, the inner left armature and front contact of relay 612, lamp 022 the outer left armature and fron` contact of relay 613, the outer left armature and back Contact of relay G15, conductor 623, to ground at the outer left armature and contact of relay 546. A circuit is also esstablished upon the energization of relay 546 for relay 550, which extends from battery, through the winding of relay 550, to ground at the outer left armature and contact of relay 546. This relay prepares circuits for the stations lamps, but since, as previously stated, the stations designation was 0, none of the stations lamp relays 521 to 525, inclusive, were operated. Therefore, no circuits for the stations lamps are conr pleted at this time by relay 550. The en tire designation of the test number 0123-0 is now displayed upon the lamps of the in dicator.

The energization of relay T upon the completion of the code impulses, opens at the back contact of its right armature the circuit previously traced through the winding of relay 505 of the indicator' control circuit and the winding of relay 411 of the testing device, allowing these relays to release. The number, however, will remain displayed on the indicator until the disconnect key 308 of the testing device is depressed. The test man, upon observing the number displayed on the indicator lamps, checks it against the number set up on the keyboard of the testing device, and if found to be accurate, proceeds to wipe yout the displayed number by depressing disconnect key 308, which is instrumental in opening the holding circuit previously traced through the windings of relay 403 and the winding of holding relay 502 of the indicator. Relay 502, upon deenergizing, disconnects ground from the holding conductors 508 and 509, thereby causing the deenergization of all operated relays of the indicator and the lestinguishing of all the lighted lamps. At the testing device relay 403 deenergizes and relay 418, which was held energized through the left normal contact of key 308,r also deenergizes. The circuits of the testing` device are now in condition for the initiation of the next test, which is now made with the second test number indicated in the foregoing table.

To initiate this test, the test man depresses the llo. 1 thousands key 333, the llo, 2 hundreds key 334, the No. 3 tens,l key, 335, the No. 4 units key n30 and the R stations key 33'?, winds the spring of the sequence switch, and depresses the starting key 300.

From this point the test proceeds in the manner previously described in connection with the first test number, and if the indicator functions accurately, the test number 12234-3u becomes displayed on the lamps of the indicator. The test man upon noting the correct display of the second test number, depresses the disconnect key 309, which causes operation at the indicator simulating those which take place as a result of the depressing of an assignment key, such as 211, of a trunk other than the one to which the display number belongs. The depression or key 309 bridges a resistance of 00 ohms around the winding of relay 403 in a circuit which may be traced from the left terminal of relay 403, conductor 310, the right normal Contact of key 308, resistance 329, the right contact of key 309, conductor 311, spring 407 of key 402 and its normal contact, conductor 408, ring of jack 103, ring strand of cord 108, ring of jack 111, conductor 119, the armature and contact of relay 505, winding of relay 551, contact of relay 504, to ground at the right armature and front Contact of relay 50T. It is to be noted that relay 507 is energized at this time since the test number has been completely rccorded on the lamp relays of the indicator. Relay 551, being of low resistance, the energization of relay 403 cannot continue and relay 403 thereupon releases, permitting relay 551 to energize in series with relay 502, which relay was energized at the initiation of the test. The circuit over which relay 551 is now energized is as follows: battery, winding of relay 502, conductorl 503, sleeve of jack 111, sleeve strand of cord 108, sleeve of jack 103, conductor 118, spring 404 of key 402, and its normal contact, conductor 405,re sistance 32S), contact of key 309, thence as previously traced through thevwinding of relay 551, to ground at the right armature and front contact of relay 507. Relay 551, upon energizing, closes an obvious circuit for relay 510, which at its inner left armature and contact locks to ground at the right armature and front contact of relay 507, and at its outer left armature and back contact and right arn'iature and back contact removes ground from the holding conductors 508 and 509, respectively, thus causing the release of all operated relays of the indicator and the wiping out of the displayed number. lf no trouble occurs on the second test number, the next test call, as shown in the foregoing table, is transmitted, until all ten of the test calls have been coinpleted, the succeeding test calls being released through the alternate employment of disconnect keys 308 and 309.

The test man thereupon depresses group key 328, thereby restoring group key 302, and repeats the ten test calls for the purpose of testing the indicator over an impulse circuit which has a lower resistance and higher potential, simulating the other extreme condition under which the indicator must function in actual service. The operation of key 328 causes the inclusion of resistance elements 312 to 316, inclusive in the impulse circuits extending through cams of the sequence switch and through the windings of relays 500, 513 and 514, these resistances having a total resistance of 2000 ohms, and the substitution of a 52 volt operating battery for the 45 volt battery 126 employedin the previous tests; The transfer from battery 126 to the 52 volt battery 127, is brought about through the operation of relay 125 over a circuit extending from battery, through the winding of this relay, the sleeve of iack 114, the sleeve of cord 106, sleeve of jack 101, conductor 128,v the right contact of key 328, to ground.

If the indicator control circuit is provided with a second marginal relay for permitting the control circuit to beV employed with trunk circuits having a wider range of loop resistance, the tests above described are again repeated with the key 401 depressed and the appropriate group keys depressed. 1f it be assumed that the marginal relay 501 of the indicator test is adjusted for operation over a range of from 800 to 1700 ohms loop resistance, then the ten test cal-ls in accordance with the foregoing table, are first established, with the key 330 depressed, and again established with the key 331 depressed. The operation of key 401 transfers conductor 423 of the impulse circuit from conductor 123, whichV as hereinbefore described is connected. through the winding of marginal relay 500, thence througlithe windings of relays 513 and 514', to conductorr129, which is connectedV over the sleeve of jack 104, sleeve of cord109, sleeveof jack 112, conductor 130, through the winding of the second marginal relay 501, and thence through the windings of relays 514 and 513. The marginal relay 501 functions inlV conjunction with relays 513 and 514 in exactly the same manner as previously described in connection with test calls employing mai ginal relay 500.

If the indicator mechanism fails to correctly indicate the number of any test call, this failure may be due to improper adjustment of either marginal relay 500 or501, or sensitive polarized relays 513 or 514,.failure of the transfer relays, or failure of the lamp relays to operate or to lock up after operation. If incorrect numbers are displayed, certain digits of which are correct with one or more of them wrong, the trouble may be due to the failure of the negatively polarized relay 514 to function properly, the inaccurate adjustment of relays 517 or 518, or

failure of the transfer relays 519, 520, 526,v

527, 528, 529, 533, 534, 537 or 511 to operate.

A comparison ofthe numbers set up on the@ relays may then be adjusted in the regularV manner by means of a relay adjusting test set.

The sensitive polarized relays 513 and 514, may if desired, be tested from the testing device. To test either of these relays key 320 is depressed to remove the shunt from around the resistance element 332 having a total resistance of 21,700 ohms, and' keys 416 and 300 are then depressed in succession. The operation of key 416 prior t'o the operation of start key 300 opens the circuit of release magnet 400 at the normal' contact of key 416 so that whenv the test is started through the operation of key 300, the sequence switch is not released at the time relay 411 energizes.,

If the negatively polarized relay 514, for

example, is to be tested, key 442 is depressed ten times, or a suficient number of times to' operate all of the transfer relays of the indicator. Upon each depression of the key, a` circuit is established for relay 514 whichmay be traced .from the non-grounded pole of battery 126, the armature and back contact of relay 125, the left armature and front contact of relay 124, ringV of jack 1115, ringA strand of cord 107, ring of jack 102, con-v ductor 427 lresistance 429, resistance 428, thc right contact of key 442, the left normalV contact of key 440, right armature and front contact of relay 411, conductor 321, resistance 332', conductor 319, group key 302, resi'stances 312 to 318,' inclusive,conductor 423,- normal contact of key 401, conductor 123, ring of jack 104, ring strand of cord 109, ring ofV jack 1-12, conductor 516, thence as. previously traced through the windingsy of relays` 500, 513 and`514', returning over conductor 122, tip of jack112, tip strand of cord 109, tip of jack 104, conductor 422, left armature and back contact of relay 413, conductor 421, outer left armature and front Contact of relay 411, right normal contact of key 440, left contact of key 442, conductor 121, to ground at jack 114. Polarized relay 514 should not operate over a circuit including resistance 332, and no lamps of the indicator should light. lf lamps of the indicator light the test man then knows that the relay 514 needs adjustment.

1f it is desired to test the positively polarized relay 513, the number 2000-0 is transmitted by employing the step-by-step 'keys 440, 441 and 442. For transmitting the thousands ydigit 2, a'positive and two negative impulses-are transmitted, and for each negative impulses are sent. Thus, for the l'lOF Cil entire number, one positive and ten negative impulses are required. For the transmission of' the first positive impulse the key 32() is maintained operated and the key 440 is depressed once, the impulse circuit extending as previously traced for testing relay 514, but with the terminals of battery 126 connected reversely therein. Following` the transmission of the single positive impulse, the key 320 is opened to remove resistance 332 from the circuit, and key 442 is then operated ten times. It the number 200G-O appears on the indicator, it is an indication that the positively polarized relay 513 has operated over a loop containing the high resistance 332 when it should not have operated, and that it is therefore out ot adjustment.

It may also be desirable to transmit impulses of a. test number more slowly than can be done through the use of the sequence switch in order that the test man may more closely observe the operation of the indicator under test. This may readily be accomplished through the operation of keys 440, 441 and 442, which for that reason may be known as the step-by-step keys. To operate an indicator step-by-step the key 416 is first operated to prevent the release of the sequence switch when the start key 300 is depressed. The start key 300 is the-n depressed, operating relays 403 and 411 as previously described. When key 416 is in its alternate position, a circuit is established for the lamp 443, which may be traced from battery, through the lamp 443, alternate contact of key 416, the inner left armature and front contact ot' relay 411, the right contacts of cam 417 (1), the left armature and back contact of relay 418, conductor 419, and to ground at key 309. Theillumination of lamp 443 signals the test man that he may proceed to transmit impulses through the operation of keys 440, 441 and 442. To send a negative impulse for operating the negatively polarized relay 514, keyI 442 is operated. To send a positive impulse for operating the positively polarized relay 513, key 440 is operated, and to send a strong impulse of either positive or negative polarity, the key 441 is operated in conjunction with either key 440 or key 442. It is to be noted that when key 441 is depressed, the high resist-ance 428 is short-circuited at the right contact of this key and the right contact of either key 44() or 442, so that the current flowing through the contacts of either key 440 or 442 and the windings of relays 500, 513 and 514 is strong enough to energize the marginal relay 500 in addition to either relay 513 or 514.

To test the indicator control circuit with respect to the accuracy with which it functions in controlling` ringing current selection, the test man successively sets up testA call numbers GOOG-J, (1000e-R, OOOO-M and OOOO-V upon the keyboard, and conducts a regular test of the control circuit for each of' these numbers in the manner previously described. For the test number @OOO-J, only stations relay 524 should be operated. With only relay 524 operated, no ground connections are made with conductors 552 and 553, and therefore no circuits are effective for relays 465 and 466 of the test, device. Vith both relays 465 and 466 deenergized, none of the lamps 467, 468 or 469 is illuminated and the test man is apprise-d ot the fact that ringing selection for the party J has been correctly performed.

For the second ringing test call, OOOOR, stations relays 521, 522 and 523 are energized, and a circuit is established Jfor relay i 465 which may be traced from battery, through the winding of relay 465, the normal Contact of key 456, the right normal contact of key 457, conductor 142, tip of jack 100, tip strand of cord 105, tip of jack 110, conductor 161, conductor 552, the left armature and front contact of relay 522, to ground at the outer right armature and front contact or" relay 523. Relay 465, upon energizing, establishes a circuit for lamp 468, which may be traced from battery, through lamp 468, right armature and front contact of relay 465, to ground at the left armature and back contact of relay 466. If lamp 468 lights, as it should, it indicates to the test man that ringing selection for the party R has been accurately performed.

For the third ringing test call in accordance with the designation OO00#M, stations lamp relay 525 only is operated, and a circuit should therefore be etective. for relay 466, which may be traced from battery, through the winding of relay 466, the right normal contact of key 458, the left normal contact of key 457, conductor 146, ring of liack 100, ring strand of cord 105, ring ot jack 110, conductor 162, conductor 553, to ground through the outer right armature and contact of relay 525. If relay 466 operates, a circuit is established for lampl 469, which may be traced from battery, through the lamp 469, the left armature and front contact of relay 446, to ground at the right armature and back contact of relay 465, indicating to the test man that ringing selection for the party M has been successfully performed.

On the fourth ringing test call for the party W ringing selection, stations relay 523 only is operated, and circuits are thereupon established for both relays 465 and 466, thecircuit of relay 465 extending, as previously traced, over conductor 552, the left armature and back contact of relay 522, to ground atv the outer right armature and contact of relay y523, and the circuit of relay 466 extending as previously traced, over conductor 553, the right armature and back contact of relay 522, the inner left armature and front contact of 'relay 523, the inner left armatures and back contacts of relays 524 and 525, to ground at the inner left armature and contacty of relay 528. W'ith both relays 465 and 466 energize-d, a circuit is established for lamp 467, which may be traced from battery, through lamp 467, the right armature and contact of relay 466 and to ground at the left armature and vcontact of relay 465. If the lamp 467 is lighted, as it should be, it is an indication to the test man that the control circuit yhas functioned properly for Vselecting ringing current for rin ing the party W ona party line.

pon the completion of the test of the indicator, thepatching cords 105 to 109 are removed from the jacks 110 to 115, inclusive, releasing the testing devicel from the indicator, and if the indicator is found to function accurately, or after adjustment is caused to function accurately, the cordrcircuits of the operators position are disconnected from the emergency indicator apparatus and connected to the indicator which has just been tested.

Testing a trunk circuit. Before proceeding to test a trunk circuit 5 the trunk is first made busy at its outgoing end so that it may not be taken for use at theV machine switchingA oiiice to which it eX- tends during the test, and the cord circuits 105 to 109, inclusive, are plugged into the jacks 100 to 10.4, inclusive, of the testing device andinto jacks 113 to 117 respectively. It will now be noted that by the connection of cord 109 to jacks 104 and 117 the testing device is connected to the tip and ring strands 206 and 207 of the incoming end of the trunk circuittobe tested. Y The test man now throws the trunk testing key 402 to its alternate position, operatesthe proper group key for applying 45 volt battery and the higherloop resistance over Which the operators indicator is designed to operate, in this instance key 302, sets up the test number 00000 on the keyboard, Winds the springvof the sequence switch, and depresses start key, 300. The designation 00000 is the oticial designation of the test line terminating beforethe operators position in jack 227, and is recognized as a test call Whenthis designation appears upon the lamps of the operators call'indicator. c

Upon the operation of key 300 a circuit is established for relay 413,` which may be traced from battery, through the right Wind ing of relay 413, conductor 444, left contact of key 300, conductor 445, alternate Contact of spring 446 of key 402, inner right armature land back contact of relay 403, conductor 410, spring 409 of key 402 and its alternate contact, conductor 447, outer right armature and back contact of relay 418, conductor 419, to ground at the normal contact of key 309. Upon the release of key 300, relay 413 locks through its inner right armature and front Contact, through the spring 446'y and its alternate contact of key 402, to ground at the contact of key 309, and at its left armature and front contact closes a circuit extending from the testing device over the strands 206 and 207 of the trunk under test, through the windings of trunk relay 200. This circuit may be traced from ground, through the left winding of relay 200, the left normal contact of relay 201, the lower left-,Winding .of repeating coil 202, thel innermost lower armatures. and back contacts of relays 204 and 205, conductor 206, ring ,of .jack 117, ring strand of cord 109, ring of jack104, conductor 123, normal contact of key 401, conductor 423, resistances 312 to 313, inclusive, left contact of key 302., conductor 319, normal contact of key 320, conductors 321 and 448, contacts of key 449, Winding of relay 451, the left armature and Contact of relay 413, conductor 422, tip of'jack 104, tip strand of cord 109, tip of jack 117, conductor207, innermost upper armatures and back contacts of relays 205 and 204, conductor 208, upper left winding of repeating coil 202, right normal contacts of relay 201, to battery through the right Winding ofrelay 200. Relays 200 and 451 both energize in this circuit, relay 451 closing a circuit eXtending from ground, through the left Winding of relay 413, the armature Vand contact of relay 451, the left Winding of relay 403, to battery at the alternate contact of spring452 of key402. Relay-403, upon operating, locks over a circuit extending from battery at spring 452, through bothof its windings, its innerwright armature andV front contact, the alternate contact of spring 409 ofv key 402, conductor 447, the outer right armature and back contact of relay 418, conductor 41,9,.to ground at the left normal con tact 0f key 309, and its inner right armature Y and back contact opens the locking circuit of relay Relay 413,hoivever, is maintained energized in series with the left Winding ofV relay 403. Y y c At the trunk circuit under test relay 200, upon energizing, closesa circuit nfor relay 209, which may be traced from battery at the Outerfright armature and back Contact of relay 210, Winding of relay 209, the right armature and back contactof relay 212, to

ground at the armaturefandContact of relay f 200. Relay 209, upon energizing, closes a locking circuit for itself extending fromrbattery, through its outer right armature and contact, its winding, and to ground at the armature and contact of relay 200, and at its inner right armature and front contact establishes a circuit for the assignment; lamp 213. This circuit may be traced from battery, through lamp 213, the left non-inductive winding of relay 214, the inner right armature and front contact of relay 209, to ground. The operator, noting the illumination ot' lamp 213, depresses the assignment key 211 associated with the trunk circuit corresponding to the lighted lamp 213, whereupon a circuit is established for the assignment relay 215. This circuit may be traced from battery, through the winding of relay 502, conductor 503, conductor 216, the lower armature and back contact of relay 217, conductoi` 218, the right winding of relay 215, the outer left armature and front contact of relay 209, the upper contact of key 211, conductor 119, the armature and contact of relay 505, conductor 506, to ground at the left armature and back contact of relay 50T. Relays 502 and 215 energize in this circuit, relay 502 connecting ground to the holding conductors 508 and 509 in the manner previously described to prepare the indicator circuits for operation.

Relay 215, upon energizing, closes a lool;- ing circuit for itself extending from battery on conductor 218, through both of its windings, to ground at the front contact of its inner left armature. Relay 215 also closes an obvious circuit for relay 210, which in turn opens the initial energizing circuit of relay 209 and closes a circuit for relay 214, which may be traced from ground, through the right winding of relay 214, the inner right 'armature and front contact of relay 210, to battery at the outer right armature and contact of relay 209. Relay 210 -also prepares a iiashing circuit for the lainp .213, which later becomes effective following the deenergization of relayr209. Vith rel'ays 214 and 215 now energized, a circuit is closed for relay 205 which may be traced from battery, through the left armature and contact of relay 214, conductor 219, winding of relay 205, conductor 220, outer left armature and contact of relay 215, conductor 120, winding of relay 505, to ground at the right 'armature and back contact of` relay 507. Relays 205 and 505 energize in this circuit, relay 205 disconnecting the windings of relay 200 from the trunk conductors 207 and 206, and extending these conductors over conductors 122 and 516, respectively, to the windings of relays 500, 513 and 514 in the manner previously described.

Upon the disconnection of relay 200 following the energization of relay 205, the locking circuit of relay 209 is opened and relay 209 deenergizes, opening the previously traced circuit of lamp 213 and connecting this lamp in a circuitextending from battery, through the left winding of relay 214, the inner right armature and back contact of relay 209, left armature and front contact of relay 210, the lower armature and back contact of relay 221, to ground through interrupter 222 for flashing the lamp 213 until the operator extends the connection by plugging up plug 223 after the line designation has been displayed on the lamps of the call indicator. Upon the deenergization of relay 209, the initial energizing circuit of relay 214 is opened at the outer right 'armature and contact of relay 209, relay 214 being now maintained energized in a holding circuit extending through its winding, its inner right armature and front contact, to battery through the winding of relay 212. Relay 212, upon'energizing in this holding circuit, opens the initial energizing circuit of relay 209 'and prepares a locking circuit for itself which is effective upon the reenergization of relay 200, as will hereinafter appear.

At the testing device, upon the disconnecM tion of relay 200 through the operation of relay 205, relay 451 deenergizes, opening the holding circuit of relay 413 which in turn deenergizes and closes a circuit for relay 411. This latter circuit may be traced from b'attery, through the winding of relay 411, conductor 412, the left armature and contact of relay 403, the outer right armature and back contact of relay 413, to ground at the uppermost altern'ate contact of key 402. Relay 411, upon energizing, closes the previously traced circuit for the sequence switch rel'ase magnet 400 to start the sequence switch, and connects the cams of the sequence switch over conductors 423 and 421 to the previously traced ciruit extending through the windings of relays 500, 513 and 514 of the operators call indicator. The sequence switch thereupon functions to transmit a series of light negative impulses for setting up the designation 00000 upon the lamp relays of the indicator, it being recalled th'at this designation was recorded by the test man upon the keyboard of the test device.

As soon as the sequence switch reaches position 18 following the transmission of all f of the code impulses, the circuit of relay 418 is established as previously described, this relay locking through its left armature and front contact, to ground at the normal cont'act of key 309. Relay 418 also opens the locking circuit of relay 403, which thereupon deenergizes, opening the circuit of relay 411. Relay 418 also closes a circuit through the supervisory lainp 438, as previously described, to indicate that the code impulses have all been transmitted. Relay 418 also connects the windings of relays 439 and 453 to the back contacts of 1'e1ay4ll for a purpose which will later appear.

CJi

At the call indicator, as soon as the last impulses have been received, the number 00000 becomes displayed upon the vindicator lamps, and relays 507 and 546 become energized in the manner previously described.

Relay 507, upon energizing opens the circuit of relays 505 and 205 thereby causing the release of these relays. Relay 205, upon deenergizing disconnects conductors 122 and 516 from the trunk conductors 207 and 206, and reconnects the trunk conductors with the windings of relay 200. Relay 200 now becomes energized in series with the windings oi relays 439 and 453 rover the following -circuit: ground, left winding of relay 200, lett normal contacts of relay 201, lower left winding of repeating coil 202, conductor 203, the innermost lower armatures and back contacts of relays 204 and 205, conductor 206, ring of jack 117, ring strandk of cord 109, ring of jack 104, conductor 123,' normal contactot key 401, conduct-or 423, resistances 312 to 318, inclusive, left contact of key' 302, conductor 319, normal contact of key 320, conductors 321 and 424right armature and back co-ntact of relay 411, inner right armature and front contact otrelay 418, right winding of relay 453,- winding of polarized relay 439, left winding of relay 453, outer lett armature and bia-ck cont-act ot' relay 411, conductor '421, lett arma-ture and back` contact of relay 413, conductor 422, tip of j ack 104, tip strand of cord 109, tip of j ack 117 conductor 207, innermost upper armatures-and bac-k contacts et relays 205 and 204, upper left windingk of relay 202, right normal contacts of relay 201, right winding' ot relay 200, to battery.

1 TWith relay 200, energized, a locking circuit is established for relay 212 in shunt ofl the right winding' of relay 214, thereby causing the deenergization ol" relay 214. Relay 214 thereupon deenergizes, opening at its left armature and front contact the initial energizingv circuit ofrelay 205. At the testing device relay 453 energizes, establishing an obvious circuit for the lamp 454, indicating to the test man that the trunk has been closed through from the testing device to the'operatos trunk circuit. Relay 439bcing polarized, is not energized at this time.-

The o}; erator, noting the illuminationi of the lamps ol` the indicator, picks up the plug 223 of the trunk circuitdesignated by the flashing lamp 213,- and tests thc sleeve of jack 227, and then inserts' the plug in the j ack. Upon the insertion ot the plug in the jack, sleeve relay 217 is energized in acircuit which may be traced from battery, through the winding. of relay 223, right armature and back contact of relay 229,

armature and back contact of relay 230,v

outer left armature and Contact of relay 212, outer right armature and back` contact oit rclay 214, winding of relay 217, sleeve of plug 223, sleeve of jack 227, conductor225,.to ground through the winding of relay 130. Lamp 224 being shunted by the winding of relay 228 does not energize at this time in series with relays 217 and 130. Relays 217 and 130 energize in this circuit, relay 217 disconnecting the tip of the plug 223 fromvconductor 226, whichy extends through the upper' armature and contact of relay 221 to the test winding of the operators head set, and connectsthe tipv of the plug to the tip strand 227 of the trunk circuit. Relay 217 at its lower armature and back contact opens the holding circuit previously traced through the windings of relays 215 and 502, whereupon these relays deenergize, relayv 502 disconnecting ground potentiall from the holding conductors 508 and 509,. thus.- releasing allA energizedi'elays of the callindicator kand extinguishingthe lightedlamps. Relay 215, upon deenergizing, opensthe circuit orelay 210, whereupon the circuit over which lamp 213 was flashed is opened.

Relay 130, upon energizing, now closes a circuit extending from ground at its armaturecontact, over conductor 131, sleeve of jack 113, sleeve strand of cord 105, sleeve of jack 100, through lamp 455, to batte-ry, and lamp 455 operates to indicate to the test man that the operator has plugged up the cord of her trunk circuit in the jack 227 of the test line.

Ringing relay 228, uponenergizing, `closes a circuit for' connecting a source-of ringing current to Athe conductors of the test line.`

Since neither ofthe ringing' selection relays 232 or 233 has been operated, the circuit4 over which ringing current is applied'inay be traced from the source of ringing current 231, through the left handwinding of inarginal ringing cut-'oill relay 230, upper armature and back Contact of relay 232, the innermost upper armature. and back Contact ot' relay 233, the lower arma-ture and front contact of ringing relay 228', ring of plug 223, ring of jack 227, conductor 234,'lettl armature and back contact oit relay 132vv conductor 133, the windings of relays 134 to 137, inclusive, in parallel, conductor 13S, the right armature and4 back- Contact ot relay 132, conductor 235, tip of jack 227, tip of plug 223, upper armature and liront Contact of relay- 217, upper armature and liront contact of relay 223, to groundat. the innermost lower armature and back Contact of relay v233. Relays-134 to 137, inclusive, energize in this circuit, but relay 230 being marginal, does not receive suiiicient current to cause its energization. Since both relays 232 and 233 are deenergized, current from the source 231 is applied to ythe ring conductor234; of the test line in such a. manner as to cause only the operation of biased ringer 139,` current from thesource 231 flowing over the. ring conductor 234 as previously traced through i 

